Chrysotile is the most cytotoxic and most commonly used asbestiform mineral. We use this asbestos type in inhalation and in vitro studies. There is good evidence that the elemental nature of this asbestos plays an important role in its cytotoxic potential. Previously, we determined the dehydrating agents and fixatives that alter the elemental content of chrysotile, and we showed that elemental changes take place in the lungs of rats that have inhaled the fibers. Now we have shown that only magnesium ions are translocated from acid-treated chrysotile fibers and no significant silicon leaching can be detected by electron beam techniques. In addition, we have initiated studies to determine in which anatomic compartment(s) of the lung the elemental content of chrysotile asbestos can be altered. Data has been collected by electron microscopic and associated X-ray energy spectrometric techniques. Anatomic regions containing inhaled asbestos are the airway, alveolar and capillary lumena, airway and alveolar epithelial cells, pulmonary macrophages and interstitial cells and connective tissue. No elemental changes (compared to the control asbestos) have been detected through the eight-day post-exposure period studied. Longer time periods after inhalation are under investigation.